<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Set集合实践</title>
</head>
<body>
    <script>
        let arr = [1, 2, 3, 4, 5, 4, 3, 2, 1];
        // 1.数组去重
        let result1 = [...new Set(arr)];
        console.log(result1);

        // 2.交集
        let arr2 = [4, 5, 6, 5, 6];
        // let result2 = [...new Set(arr)].filter(item => {
        //     let s = new Set(arr2);
        //     return !!s.has(item);
        // })
        let result2 = [...new Set(arr)].filter(item => new Set(arr2).has(item))
        console.log(result2);

        // 3.并集
        let union = [...new Set([...arr, ...arr2])];
        console.log(union);

        // 4.差集
        let diff = [...new Set(arr)].filter(item => !(new Set(arr2).has(item)))
        console.log(diff);
    </script>
</body>
</html>